feat: add TopFieldError interface to expose parent struct reflection

.gitignore

@@ -30,3 +30,4 @@ _testmain.go
 cover.html
 README.html
 .idea
+.vscode

errors.go

@@ -157,8 +157,16 @@ type FieldError interface {
 	Error() string
 }
 
+type TopFieldError interface {
+	FieldError
+
+	// Top returns the actual field's parent value in case needed for creating custom the error
+	Top() reflect.Value
+}
+
 // compile time interface checks
 var _ FieldError = new(fieldError)
+var _ TopFieldError = new(fieldError)
 var _ error = new(fieldError)
 
 // fieldError contains a single field's validation error along
@@ -176,6 +184,7 @@ type fieldError struct {
 	param          string
 	kind           reflect.Kind
 	typ            reflect.Type
+	top            reflect.Value
 }
 
 // Tag returns the validation tag that failed.
@@ -274,3 +283,9 @@ func (fe *fieldError) Translate(ut ut.Translator) string {
 
 	return fn(ut, fe)
 }
+
+// Top returns the actual field's parent value in case needed for creating custom the error
+// message
+func (fe *fieldError) Top() reflect.Value {
+	return fe.top
+}

struct_level.go

@@ -135,6 +135,7 @@ func (v *validate) ReportError(field interface{}, fieldName, structFieldName, ta
 				structfieldLen: uint8(len(structFieldName)),
 				param:          param,
 				kind:           kind,
+				top:            v.top,
 			},
 		)
 		return
@@ -153,6 +154,7 @@ func (v *validate) ReportError(field interface{}, fieldName, structFieldName, ta
 			param:          param,
 			kind:           kind,
 			typ:            fv.Type(),
+			top:            v.top,
 		},
 	)
 }

validator.go

@@ -136,6 +136,7 @@ func (v *validate) traverseField(ctx context.Context, parent reflect.Value, curr
 						structfieldLen: uint8(len(cf.name)),
 						param:          ct.param,
 						kind:           kind,
+						top:            v.top,
 					},
 				)
 				return
@@ -161,6 +162,7 @@ func (v *validate) traverseField(ctx context.Context, parent reflect.Value, curr
 						param:          ct.param,
 						kind:           kind,
 						typ:            current.Type(),
+						top:            v.top,
 					},
 				)
 				return
@@ -415,6 +417,7 @@ OUTER:
 								param:          ct.param,
 								kind:           kind,
 								typ:            typ,
+								top:            v.top,
 							},
 						)
 
@@ -435,6 +438,7 @@ OUTER:
 								param:          ct.param,
 								kind:           kind,
 								typ:            typ,
+								top:            v.top,
 							},
 						)
 					}
@@ -475,6 +479,7 @@ OUTER:
 						param:          ct.param,
 						kind:           kind,
 						typ:            typ,
+						top:            v.top,
 					},
 				)
 

validator_test.go

@@ -355,7 +355,7 @@ func TestStructLevelInvalidError(t *testing.T) {
 	validate.RegisterStructValidation(StructLevelInvalidError, StructLevelInvalidErr{})
 
 	var test StructLevelInvalidErr
-
+	val := reflect.ValueOf(test)
 	err := validate.Struct(test)
 	NotEqual(t, err, nil)
 
@@ -371,6 +371,10 @@ func TestStructLevelInvalidError(t *testing.T) {
 	Equal(t, fe.ActualTag(), "required")
 	Equal(t, fe.Kind(), reflect.Invalid)
 	Equal(t, fe.Type(), reflect.TypeOf(nil))
+	top, ok := fe.(TopFieldError)
+	Equal(t, ok, true)
+	Equal(t, top.Top().Kind(), val.Kind())
+	Equal(t, top.Top().Type().Name(), val.Type().Name())
 }
 
 func TestNameNamespace(t *testing.T) {